Books like The Hunt For The Hundredth Key
Gerónimo Stilton
The Hunt For The Hundredth Key is 128 pages, about 2 hours 21 minutes at 250 words a minute.
7 books to read next
How long each takes
Castle 1.4 h 
Cam Jansen and the Catnapping Mystery 1.1 h 
Castle 35 min 
Ms. Frizzle's Adventures 44 min 
Castle 1.3 h 
Knights and Castles 2.2 h 
Avoid Being a Prisoner in a Medieval Dungeon! 35 min Bar height shows length. Estimated at 250 words a minute.